Sarah Lancashire has received a lot of fan mail in the two decades since she first won viewers’ hearts playing dippy but lovable blonde barmaid Raquel Watts in Coronation Street.

She’s gone on to become a TV favourite playing highly emotional roles including portraying Angela Cannings, a woman wrongly convicted of murdering her two baby sons, a social worker-turned-child snatcher and the mum of a murdered prostitute.

But Sarah, 49, has never received quite so many moving and uplifting letters as she has since her award-winning starring role in the surprise hit of 2012, Last Tango in Halifax.

In it she plays a troubled headmistress who finds love with a female colleague.

“People have absolutely taken the show to heart,” she says of the Bafta-nominated series which returns to BBC1 tonight.

“And the nature of the role that I play, Caroline, has clearly hit a nerve with a lot of people. I’ve had a lot of lovely feedback from women in their mid-life who have found themselves in similar circumstances, or are just embarking on same-sex relationships.

“Their feedback has been that the sensitivity has been beautiful, they haven’t seen that nature of the relationship portrayed or written in such a sensitive manner before.

Tough: Sarah as wrongly accused mum Angla Cannings (Image: BBC)

“Because it’s never salacious – it’s not there to shock – it’s really, really beautifully done. People maybe find it easier to write to you because they don’t know you, and so they know that they’re not going to be judged, but there have been very honest and very open letters from women.

“There was one lady who made her mum sit down and watch the entire series, and then came out to her.

“That gets me – I think ‘Wow, what a lovely thing that we managed to make somebody’s transition easier.’

“I try and write back to as many people as possible. People have stopped me in the street and said ‘thanks’.

‘You don’t always realise the impact you have on people’s lives. You just think ‘I’m an actor, I don’t think I’m doing anything particularly important in life’ and then you suddenly realise that actually for a fleeting moment you do make a difference to somebody’s life – it has an impact.”

The romantic drama, written by Sally Wainwright, follows former childhood sweethearts Alan and Celia, played by Sir Derek Jacobi and Anne Reid, as they embark on a relationship after reuniting in their 70s.

It also charts the troubled goings-on in the lives of Celia’s daughter Caroline and Alan’s daughter Gillian (played by Nicola Walker).

As dark as it is comic, the drama proved a huge hit with both critics and viewers of all ages when it was first shown late last year.

Happily married: Sarah and husband Peter Salmon (Image: PA)

Lancashire-born Sarah, who is married to TV executive Peter Salmon and has three sons, two from a previous marriage, says: “My kids love it. Two kids aren’t really kids any more, they’re grown up, but I’ve got a 10-year-old, and he loves it, as do all their friends.

“It doesn’t surprise me that it appeals to every generation, because we’ve all had parents, we’ve all had grandparents, we can all relate to a multi-generational family.”

But Sarah admits that her character’s gay storyline came as a surprise when it was revealed to her halfway through filming series one.

“I had no idea,” she says. “The director phoned me and said, ‘I think you ought to know this’ and that was a huge shock.

“But I approached Caroline as any human being. I don’t look at her gender, I don’t look at her sexuality, I just try to view the humanity of her that is on the page.

“I’m straight, but it’s immaterial what your sexuality is. Isn’t it really just about being a fulfilled human being? That’s what Sally’s captured so brilliantly.

“Love is love. It doesn’t matter about sexuality, it’s just about how you feel towards somebody else and being good and honest with them.”

But Sarah hints that Caroline does face some tough times in series two and at one point is “almost at rock bottom”.

She says: “She isn’t out and proud yet. It’s still very much a clandestine relationship, she hasn’t quite found the courage to just step out the wardrobe, and go, ‘Here I am, and this is me.’ She has to be taken on quite a journey.

“It’s very rare to find a gay character on television and the one thing that you don’t want is for this character to be portrayed inaccurately. There was never any moment when I looked at the scripts and thought, ‘that’s a bit dodgy’ – Sally just has it all.”

It’s hard to believe Sarah left Coronation Street as long ago as 1996 (although she came back for one last episode in 1999) because fans still remember Raquel and Curly Watts’ love story with real affection.

She says of the role: “I’ve escaped it – it’s everybody else who hasn’t. If I hadn’t escaped it that would have been a problem mentally.

“It was fun, and I loved the character I created, it was lovely to do, but you literally have to move on from something if you intend to have a career beyond it.

When I left the Street it was like jumping off a cliff at midnight, because I didn’t know how it was going to affect me, whether it was going to be detrimental.

“I have always tried just to continue working and I’m very grateful that I’m still continuing to do a job I love. But it’s only part of my life, I’m a mum and a wife, and a daughter... and I love it.”

Sarah says it was “the easiest decision of my political life” to return to Last Tango – despite a tough four-and-a-half month filming schedule – and she says the second series is “great, absolutely terrific stuff”.

“We are a very small company of actors really, and we just all get on... more than get on, we care for each other,” she says.

“Anne and Derek stay at the hotel together, so I think they have supper every night together but we don’t socialise – you just can’t when you’re working 15-hour days, unless of course you’re 19. I’m in bed at nine, with the dog.

“It’s not a case of being exhausted, it’s just a case of pacing yourself.

It is demanding, but it’s not a hardship because it’s so stimulating.

“As an actor you can wait an entire career to be involved in a project like this.

“When it comes along you are terribly, terribly lucky to be invited on board.”